Developer composition for lithographic printing plate

ABSTRACT

A developer composition for a lithographic printing plate comprising on an aluminum plate support a photosensitive layer which comprises an ethylenically unsaturated monomer, a photopolymerization initiator and a polymeric binder is disclosed, wherein the developer composition contains water in an amount of not more than 10% by weight and is substantially free from a silicate. There is also disclosed a developer solution obtained by dissolving the developer composition in water.

FIELD OF THE INVENTION

[0001] The present invention relates to a developer composition forlithographic printing plates.

BACKGROUND OF THE INVENTION

[0002] Alkali metal silicate developers have been extensively used todevelop photosensitive lithographic printing plates. In thephotosensitive layer of a conventional photosensitive lithographicprinting plate, ortho-quinoneazide compounds are used in combinationwith novolak resin and an aqueous alkaline silicate solution capable ofdissolving novolak resin is used as a developer. A developer has a pH ofabout 13 to dissolve the novolak resin of the photosensitive layer sothat silicates exhibiting superior buffer capacity at a pH near 13 havebeen allowed to be contained in the developer to enhance stability, asdescribed in, for example, JP-A No. 8-160633 (hereinafter, the term,JP-A refers to Japanese Patent Application Publication).

[0003] Such a developer is liquid and so heavy, imposing a burden on theperson handling them so that there have been widely proposedconcentrated developers having a reduced water content. However,silicate-containing developers tend to easily solidify with reduction ofthe water content and even when re-diluted with water again, it is noteasily dissolved in water, leading to insufficient concentration. Toovercome such a problem, solidifying the silicate-containing developerin a granular form was proposed, as described in JP-A Nos. 5-142786(pages 1-8), 6-266062 (pages 1-5) and 7-13341 (page 8). However, it wasdifficult to achieve stable solidification of the silicate, resulting inincreased manufacturing costs and being of no practical advantage.

[0004] In a photopolymerization type photosensitive layer containingethylenically unsaturated compounds, as represented by a photopolymertype CTP plate, on the other hand, novolak resin is not generally used,making it possible to design a developer at a pH of less than 12.5 andit has also no need to use a silicate as a pH buffer, rendering itpossible to design a developer containing no silicate. In suchdevelopers described in the disclosure (for example, JP-A No.2002-251019, page 34), there has not been proposed solidification of adeveloper component or a concentrate having a relatively highconcentration factor. A developer for use in a photopolymer type CTPplate generally needs a higher developer-replenishing rate thanconventional photosensitive lithographic printing plates which containortho-quinoneazide, and thus a lightweight developer has been desired.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide a developercomposition and a developer replenisher composition for a lithographicprinting plate which are lightweight, easy-to-use and produces noproblem such as being indissoluble when diluted with water.

[0006] The foregoing object of the invention can be achieved by thefollowing constitution:

[0007] 1. A developer composition for a lithographic printing platecomprising on the surface of an aluminum plate support a photosensitivelayer of a photopolymerization type photosensitive resin compositionwhich comprises an ethylenically unsaturated monomer, aphotopolymerization initiator and a polymeric binder, wherein thedeveloper composition has a water content of 10% by weight or less andthe developer composition being substantially free from a silicate.

[0008] 2. A developer solution for a lithographic printing platecomprising on an aluminum plate support a photosensitive layer whichcomprises an ethylenically unsaturated monomer, a photopolymerizationinitiator and a polymeric binder, wherein the developer solution isobtained by dissolving the developer composition described above inwater.

[0009] Further, the present invention concerns a method for preparing aplanographic printing plate using the developer solution describedabove. Thus, the method comprises imagewise exposing the lithographicprinting plate described above and developing the exposed lithographicprinting plate in the developer solution to obtain a planographicprinting plate.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The developer composition according to this invention may beprepared by forming a developer solution, followed by evaporation todryness and is preferably prepared in such a manner that pluralcomponent materials are mixed with a small amount of water or withoutany water to make a concentrated material. Thus, the developercomposition may be in the form of a paste or a powdery mixture. Thedeveloper composition can also be prepared in the form of granules ortablets, as described in JP-A Nos. 51-61837, 2-109042, 2-109043,3-39735, 5-142786, 6-266062 and 7-13341.

[0011] The developer composition may be divided into plural partsdiffering in material species or compounding ratio. The thusconcentrated developer composition is used for development preferably bydissolving in or dilution with water to a prescribed concentration priorto development. In cases when the developer composition is used as areplenisher, it is preferred that the developer composition is dissolvedin or diluted with water to a prescribed concentration, followed bybeing supplied to a developer working solution, whereby it is alsofeasible to supply a developer at a higher concentration than theprescribed one or, without being diluted to the prescribedconcentration, to the developer working solution. When supplied at ahigher concentration than the prescribed one or without being diluted tothe prescribed concentration, water may be separately added in the sametiming or in a different timing.

[0012] The developer composition according to this invention has a watercontent of not more than 10% by weight, and preferably not more than 1%by weight, based on the composition. The higher water content oftencauses problems such that developer components separate out in water,losing homogeneity or becomes liquid, making handling hard.

[0013] Component materials contained in a developer solution forconventional lithographic printing plates can be employed as a materialfor the developer composition and it is preferred to exclude a materialwhich reacts at a water content of not more than 10% by weight andcannot be recovered even with dilution, a material having a largemoisture content or a liquid material at ordinary temperature. Forexample, a silicate petrifies at a reduced water content and becomeshard to be solved.

[0014] The developer composition of this invention is substantially freefrom a silicate. Thus, the developer composition contains a silicate inan amount of not more than 0.5% (preferably 0%) by weight, based on thecomposition, in which the amount of the silicate is represented byequivalent converted to SiO₂, i.e., in terms of weight converted toSiO₂. The composition preferably contains no silicate. Silicates aregenerally comprised of silicon dioxide and metal oxide, represented byxM₂O.ySiO₂. Silicates are derived from orthosilicate (M₄SiO₄), andmetasilicate (M₂SiO₃), which may combine to form polysilicates. Specificexamples of a silicate include sodium silicate, potassium silicate andammonium silicate.

[0015] Accordingly, it is preferred to use carbonates, phosphates ororganic acid salts in place of silicates.

[0016] Next, components of the developer composition of this inventionwill be explained. Unless otherwise noted, the explanation is for boththe developer composition and developer replenisher concentrate relatingto this invention. In cases when described as a developer, it refers toa developer solution or developer replenishing solution which can beobtained by dilution with a prescribed amount of water.

[0017] The developer composition or developer solution relating to thisinvention comprises an alkali reagent (alkali or alkaline material).Alkali reagents other than silicates are preferred, including inorganicand organic alkali reagents. Examples of an inorganic alkali reagent (orinorganic alkaline compound) include sodium tertiary phosphate,potassium tertiary phosphate, ammonium tertiary phosphate, sodiumcarbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate,sodium borate, potassium borate, ammonium borate, sodium hydroxide,potassium hydroxide, ammonium hydroxide, and lithium hydroxide. Examplesof an organic alkali reagent (or organic alkaline compound) includemonomethhylamine, dimethylamine, trimethylamine, monoethylamine,diethylamine, triethylamine, monoisobutylamine, diisobutylamine,triisobutylamine, n-butylamine, monoethanolamine, diethanolamine,triethanolamine, monoisopropanolamine, diisopropanolamine,ethyleneimine, ethylenediamine, pyridine, and tetramethylammoniumhydroxide.

[0018] The alkali reagents can be used alone or in combination thereof.An alkali reagent is used preferably in an amount giving a pH of 9 to13.5 (more preferably 10.0 to 12.5) and an electric conductivity of 2 to40 mS/cm (more preferably 3 to 30 mS/cm, and still more preferably 5 to20 mS/cm) when used as a developer (or developer solution). A pH lowerthan the foregoing range results in no image formation and a pHexceeding the foregoing range often causes over-development, leading toincreased damages in development of exposed areas. A conductivity lowerthan the foregoing range usually renders difficult dissolution ofphotosensitive composition provided on the surface of an aluminum platesupport, leading to stained printing. A conductivity exceeding theforegoing range results in an increased salt concentration, retardingdissolution of the photosensitive layer and resulting in layer residuesin unexposed areas.

[0019] The developer composition according to this invention preferablycontains a compound comprising a nonionic surfactant containing apolyoxyalkylene ether group, which is hereinafter also denoted apolyoxyalkylene ether compound. Addition of such a surfactant promotesdissolution of the photosensitive layer in the unexposed area andreduces penetration of a developer to the exposed area. Preferredsurfactants which comprises a polyoxyalkylene ether group include acompound represented by the following formula (1):

R₁—O—(R₂—O)_(n)H  formula (1)

[0020] wherein R₁ is an alkyl group having 3 to 15 carbon atoms, anaromatic hydrocarbon group having 6 to 16 carbon atoms or an aromaticheterocyclic group having 4 to 15 carbon atoms, each of which may besubstituted (and examples of a substituent include an alkyl group having1 to 20 carbon atoms, halogen atom such as Br, Cl or I, aromatichydrocarbon group having 6 to 15 carbon atoms, aralkyl group having 7 to17 carbon atoms, alkoxy group having 1 to 20 carbon atoms,alkoxy-carbonyl group having 2 to 20 carbon atoms and acyl group having2 to 15 carbon atoms); R₂ is an alkylene group having 1 to 100 carbonatoms, which may be substituted (and examples of a substituent includean alkyl group having 1 to 20 carbon atoms and aromatic hydrocarbongroup having 6 to 15 carbon atoms); and n is an integer of 1 to 100.

[0021] In the foregoing formula (1), the portion of (R₂—O)_(n) may becomprised of a combination of two or three groups. Specific examplesthereof include a random combination of an ethylene oxy group and apropyleneoxy group, an ethylene oxy group and an isopropyleneoxy group,an ethylene oxy group and butyleneoxy group, an ethylene oxy group andan isobutyleneoxy group, and their random or blocked linkage.Surfactants containing a polyoxyalkylene ether group, which may be usedalone or in their combination, are added to a developer, preferably inan amount of 1 to 30%, and more preferably 2 to 20% by weight. A lesseraddition amount lowers developability and an excessive amount results inincreased damages in development, leading to reduced press life of theprinting plate.

[0022] There may be incorporated other surfactants. Specific examplesthereof include nonionic surfactants including polyoxyethylene alkylethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl etherand polyoxyethylene stearyl ether; polyoxyethylene alkylaryl ethers suchas polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenylether; polyoxyethylene alkyl esters such as polyoxyethylene stearate;sorbitan alkyl esters such as sorbitan monolaurate, sorbitanmonostearate, sorbitan distearate and sorbitan trioleate; monoglyceridealkyl esters such as glycerol monostearate and glycerol monooleate:anionic surfactants including alkylbebzenesulfonates such as sodiumdodecylbenzenesulfonate; alkylnaphthalenesulfonates such as sodiumbutylnaphthalenesulfonate, sodium pentylnaphthalenesulfonate, sodiumhexylnaphthalenesulfonate and sodium octylnaphthalenesulfonate;alkylsulfates such as sodium laurylsulfate; alkyl sulfonates such assodium dodecylsulfonate; sulfosuccinic acid esters such as sodiumdilaurylsulfosuccinate: amphoteric surfactants including alkylbetainessuch as laurylbetaine and allylbetaine; and amino acids. Of thesesurfactants, anionic surfactants such as alkylnaphthalenesulfonates arespecifically preferred. These surfactants may be used alone on in theircombination. These surfactants are preferably contained in an effectiveamount (in terms of solids) of 0.1 to 20% by weight.

[0023] In addition to the components described above, the developercomposition of this invention may optionally contain additives such asan organic solvent, chelating agent, reducing agent, dye, pigment,water-softening agent, antiseptic agent and defoaming agent.

[0024] The developer composition used in this invention preferablycontain various development stabilizers. Preferred examples thereofinclude a polyethylene glycol adduct of a sugar alcohol,tetraalkylammonium salts such as tetrabutylammonium hydroxide,phosphonium salts such as tetrabutylphosphonium bromide, and iodoniumsalts such as diphenyliodonium chloride, as described in JP-A No.6-282079; anionic surfactants and amphoteric surfactants described inJP-A No. 50-51324; water-soluble cationic polymers described in JP-A No.55-95946; water-soluble amphoteric polymer electrolytes described inJP-A No. 56-142528; alkylene glycol adducts of organic boron compoundsdescribed in JP-A No. 59-84241; polyoxyethylene-polyoxypropylene blockpolymer type water-soluble surfactants described in JP-A No. 60-111246;polyoxyethylene-polyoxypropylene-substituted alkylenediamine compoundsdescribed in JP-A No. 60-129750; polyethylene glycols having aweight-average molecular weight of 300 or more, described in JP-A No.61-215554; fluorinated surfactants containing a cationic group describedin JP-A No. 63-175858; water-soluble ethyleneoxide adducts obtained byaddition of at least 4 mol of an ethyleneoxide to an acid or alcohol, asdescribed in JP-A No. 2-39157; and water-soluble polyalkylene compounds.

[0025] The developer or developer replenishing solution used in thisinvention is optionally added with organic solvents. Such aorganicsolvents are suitably selected from those exhibiting a solubility inwater of about not more than 10% by weight (preferably not more than 5%by weight). Examples thereof include 1-phenylethanol, 2-phenylethanol,3-phenyl-1-propanol, 4-phenyl-1-butanol, 4-phenyl-2-butanol,2-phenyl-1-butanol, 2-phenoxyethanol, 2-benzyoxyethanol, o-methoxybenzylalcohol, m-methoxybenzyl alcohol, p-methoxybenzyl alcohol, benzylalcohol, cyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol,4-methylcyclohexanol, N-phenylethanolamine, and N-phenyldiethanolamine.The foregoing organic solvents are contained at 0.1 to 5% by weight ofthe total weight of a developer, preferably are substantially notcontained, and more preferably not contained at all. Herein, theexpression, substantially not contained means being 1% by weight orless.

[0026] The developer composition used in this invention is optionallyadded with a reducing agent. Such a reducing agent prevents staining ofprinting plates and is effective, specifically when developing anegative type lithographic printing plate containing a photosensitivediazonium salt compound. Preferred organic reducing agents include, forexample, phenol compounds such as thiosalicylic acid, hydroquinone,metol, methoxyquinone, resorcin and 2-methylresorcin; and aminecompounds such as phenylenediamine and phenylhydrazine. Preferredinorganic reducing agents include sodium, potassium and ammonium saltsof inorganic acids such as sulfurous acid, hydrogensulfurous acid,phosphorous acid, hydrogenphosphorous acid, dihydrogenphosphorous acid,thiosulfuric acid, and dithionous acid. Of these reducing agents, asulfite exhibits superior anti-staining effects. The reducing agent iscontained in the developer working solution in an amount of 0.05 to 5%by weight.

[0027] The developer composition used in this invention may optionallybe added with an organic carboxylic acid. Such an organic carboxylicacid is an aliphatic carboxylic acid and aromatic carboxylic acid having6 to 20 carbon atoms. Specific examples of an aliphatic carboxylic acidinclude caproic acid, enathylic acid, caprylic acid, lauric acid,myristic acid, palmitic acid and stearic acid. Alkanoic acids having 8to 12 carbon atoms is specifically preferred. There are also usableunsaturated fatty acids containing a double bond in the carbon chain orbranched fatty acids. The aromatic carboxylic acid refers to acarboxyl-substituted benzene, naphthalene or anthracene ring compoundand specific examples thereof include o-chlorobenzoic acid,p-chlorobenzoic acid, o-hydroxybenzoic acid, p-hydroxybenzoic acid,o-aminobenzoic acid, p-aminobenzoic acid, 2,4-dihydroxybenzoic acid,2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid,2,3-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid,1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid,2-hydroxy-1-naphthoic acid, 1{circumflex over ( )}naphthoic acid, and2-naphthoic acid. Of these, hydroxynaphthoic acids are effective. Theforegoing aliphatic or aromatic carboxylic acid is used preferably inthe form of a sodium salt, potassium salt or ammonium salt to enhancewater-solubility. The amount of an organic carboxylic acid contained ina developer is not specifically limited. A content less than 0.1% byweight cannot achieve sufficient effects and a content more than 10% byweight not only achieves further enhanced effects but also inhibitsdissolution of other compounds used in combination. Accordingly, thecontent is preferably 0.1 to 10%, and more preferably 0.5 to 4% byweight.

[0028] The developer composition used in this invention may be addedwith additives described below to enhance developability. Examplesthereof include neutral salts such as NaCl, KCl and KBr described inJP-A No. 58-75152; complex salt such as [Co(NH₃)₆]Cl₃ described in JP-ANo. 59-121336; amphoteric polymer electrolytes such as copolymer ofvinylbenzyl trimethylammonium chloride and sodium acrylate, as describedin JP-A No. 56-142258; organometallic surfactants containing metal suchas Si and Ti, described in JP-A No. 59-75255; and organic boroncompounds described in JP-A No. 59-84241. The developer or replenisherused in this invention may optionally contain an atiseptic, coloringagent, thickener, defoaming agent or water-softening agent. Examples ofa defoaming agent include mineral oils, vegetable oils, alcohols,surfactants and silicone, as described in JP-A No. 2-244143. Examples ofa water-softening agent include a polyphosphoric acid and its sodium,potassium and ammonium salts; aminopolycarboxylic acids such asethylenediamine-tetraacetic acid, diethylenetriaminepentaacetic acid,ethylenediaminedisuccinic acid, methyliminodiacetic acid,β-alanineacetic acid, triethylenetetraminehexaacetic acid,hydroxyethylethylenediaminetriacetic acid, nitrilotriacetic acid,1,2-diaminocyclohexanetetraacetic acid,1,3-diamino-2-propanoltetraacetic acid and their sodium potassium andammonium salts; aminotri(methylenephosphonic acid),ethylenediaminetetra(methylenephosphonic acid),diethylenetriaminepenta(methylenephosphonic acid),triethylenetetraminehexa(methylenephosphonic acid),hydroxyethylethylenediaminetri(metylenephosphonic acid),1-hydroxyethane-1,1-diphosphonic acid and their sodium, potassium andammonium salts. The optimum amount of such a water-softening agent isvariable, depending on chelating ability, and hardness and the amount ofhard water used. In general, the content thereof is 0.01 to 5% byweight, and preferably 0.01 to 0.5% by weight, based on the developer. Acontent less than the foregoing range does not achieve the intendedeffects and a content exceeding the foregoing range often adverselyaffects image portions, such as color-missing.

[0029] An automatic processor usable in this invention is providedpreferably with a mechanism for automatically replenishing a developerreplenishing solution at an intended replenishing rate to a developingtank, preferably with a mechanism for discharging a developer exceedinga prescribed quantity, preferably with a mechanism of automaticallyreplenishing water at an intended amount to a developing tank,preferably with a mechanism of detecting passing plates, preferably witha mechanism of estimating the processed plate area based on detection ofpassing plates, preferably with a mechanism of controlling thereplenishing rate of replenisher and/or water, and/or replenishingtiming based on detection of passing plate and estimation of processingareas; preferably with a mechanism of controlling the developertemperature, preferably with a mechanism of detecting pH and/orconductivity of a developer, and preferably with a mechanism ofcontrolling a replenishing rate of replenisher and/or water and/orreplenishing timing based on the detected pH and/or conductivity. It isalso preferred to provide a mechanism of diluting the developercomposition of this invention with water or dissolving the developercomposition in water, while stirring. In cases where the developing stepis followed by a washing step, used washing water is usable as dilutionwater or to dissolve the developer composition.

[0030] An automatic processor used in this invention may be providedwith a pre-processing section to allow the plate to be dipped into apre-processing solution prior to development. The pre-processing sectionis provided preferably with a mechanism of spraying a pre-processingsolution onto the plate surface, preferably with a mechanism ofcontrolling the pre-processing solution at a temperature within therange of 25 to 55° C., and preferably with a mechanism of scrubbing theplate surface with a roller-type brush. Water and the like are employedas a pre-processing solution.

[0031] The plate which has been processed with a developer ispost-processed with a rinsing solution containing a surfactant, afinisher mainly containing gum arabic or starch derivatives, or aprotective gum solution. Post-processing of the lithographic printingplate relating to this invention can be performed by the combination ofthe foregoing post-processes. For example, after completion ofdevelopment and washing, processing with a surfactant-containing rinsingsolution or processing with a finisher solution is preferred in terms ofthe rinsing solution or finisher being less exhausted. Cascadedcounter-current processing with a rinsing solution or a finisher is alsoa preferred embodiment. Post-processing is carried out using anautomatic processor provided with a developing section and apost-processing section. Post-processing is performed by spraying aprocessing solution through a nozzle or by dipping the plate into aprocessing tank filled with a processing solution while beingtransported. There is also known a method in which, after development, agiven amount of washing water is supplied to the plate surface toperform washing and waste liquor is reused as diluting water for thedeveloper composition. Processing can be performed with replenishing therespective replenishing solutions to the respective processing solutionsin accordance with processing volume or processing time. There is alsoapplicable post-processing with substantially unused post-processingsolution, a so-called a non-reusable processing system. The lithographicprinting plate which has been subjected to the foregoing process istransferred to an offset printing machine used for printing.

[0032] Gum solution may be suitably added with acids or buffers toremove alkaline ingredients in the developer. Further, there may beadded a hydrophilic polymer compound, chelating agent, lubricant,atiseptic and solubilizing agent. Inclusion of a hydrophilic polymercompound in the gum solution provides a function as a protecting agentto prevent the developed plate from flawing or staining.

[0033] Addition of a surfactant to the gum solution used in thisinvention improves the surface of the photosensitive layer. Usablesurfactants include anionic surfactants and/or nonionic surfactants.Examples of anionic surfactants include fatty acid salts, abietic acidsalts, hydroxyalkanesulfonates, alkanesulfonates,dialkylsulfosuccinates, straight chain alkylbebzenesulfonates, branchedalktlbebzenesulfonates, alkylnaphthalenesulfonates,alkylphenoxypolyoxyethylene propylsulfonates, polyoxyethylenealkylsulfophenyl ether, polyoxyethylene aryl ether sulfonic acid salts,polyoxyethylene-naphthyl ether sulfonic acid salts,N-metyl-N-oleyltaurine sodium salts, petroleum sulfonic acid salts,nitrated castor oil, sulfated tallow oil, fatty acid alkyl estersulfuric acid ester salts, alkylnitrates, polyoxyethylene alkyl ethersulfuric acid ester salts, fatty acid monoglyceride sulfate ester salts,polyoxyethylene alkylphenyl ether sulfuric acid salts, alkylphosphateester salts, polyoxyethylene alkyl ether phosphoric acid ester salts,polyoxyethylene alkylphenyl ether phosphoric acid ester salts, partiallysaponified styrene anhydrous maleic acid copolymer, partially saponifiedolefin-anhydrous maleic acid copolymer, and naphthalenesulfonateformaline condensates. Of the foregoing, dialkylsulfosuccinates,alkylsulfates and alkylnaphthalenesulfonates are preferred.

[0034] Examples of nonionic surfactants include polyoxyethylene alkylethers, polyoxyethylene alkylphenyl ethers,polyoxyethylene-polyoxypropylene block polymers, polyoxyethylene arylethers, polyoxyethylene naphthyl ethers, polyoxyethylenepolystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers,glycerin fatty acid partial esters, sorbitan fatty acid partial esters,pentaerythritol fatyy acid partial esters, propylene glycol monofattyacid esters, sugar fatty acid partial esters, polyoxuethylen sorbitanfatty acid partial esters, polyoxyethylene sorbitol fatty acid partialesters, polyethylene glycol fatty acid partial esters, polyglycerinfatty acid partial esters, polyoxyethylene-modified caster oils,polyoxyethylene grycerin fatty acid partial esters, fatty aciddiethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylenealkylamine, triethanolamine fatty acid esters and trialkylamineoxides.Of the foregoing, polyoxyethylene alkylphenyl ethers andpolyoxyethylene-polyoxypropylene block polymers are preferred. There arealso usable fluorinated or silicone-type anionic or nonionicsurfactants.

[0035] The foregoing surfactants may be in their combination. Forexample, a combination of at least two different anionic surfactants ora combination of at least one anionic surfactant and at least onenonionic surfactant is preferred. The surfactant content is notspecifically limited and preferably 0.01 to 20% by weight ofpost-processing solution.

[0036] In addition to the foregoing ingredients, the gum solution usedin this invention may contain polyhydric alcohols, alcohols or aliphatichydrocarbons, as a wetting agent. Examples of preferred polyhydricalcohols include ethylene glycol diethylene glycol, triethylene glycol,propylene glycol, tetraethylene glycol, polyethylene glycol, glycerin,and sorbitol. Preferred alcohols include, for example, alkyl alcoholssuch as propyl alcohol, butyl alcohol, pentanol, hexanol, butanol, andoctanol; and alcohols containing an aromatic ring, such as benzylalcohol, phenoxyethanol, and phenylaminoethyl alcohol.

[0037] Such a wetting agent is contained in the composition preferablyat 0.1 to 50%, and more preferably 0.5 to 3.0% by weight. The wettingagents may be used alone or in combination thereof.

[0038] There may be contained a variety of hydrophilic polymers for thepurpose of enhancing film-forming ability. Any hydrophilic polymer whichhas been usable in gum solution is suitably usable. Examples thereofinclude gum Arabic, cellulose derivatives (e.g., carboxymethylcellulose, carboxymethyl cellulose, methyl cellulose) and their modifiedcompounds, polyvinyl alcohol and its derivatives, polyvinyl pyrrolidone,polyacrylamide and its copolymers, poly[(vinyl methylether)-co-(anhydrous maleic acid)], poly[(vinyl acetate)-co-(anhydrousmaleic acid)], and poly[styrene-co-(anhydrous maleic acid)].

[0039] The gum solution relating to this invention is advantageouslyused within the acidic range of a pH of 3 to 6. Mineral acids, organicacids or inorganic salts are added to the post-processing solution toadjust the pH to the range of 3 to 6, preferably in an amount of 0.01 to2% by weight. Mineral acids include, for example, nitric acid, sulfuricacid, phosphoric acid and metaphosphoric acid. Organic acids include,for example, citric acid, acetic acid, oxalic acid, malonic acid,p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid,levulinic acid, phytic acid and organic phosphonic acid. Inorganic saltsinclude, for example, magnesium nitrate, primary phosphate, secondaryphosphate, nickel sulfate, sodium hexamethanate, and sodiumtripolyphosphate. Mineral acids, organic acids and inorganic salts maybe used alone or in combination thereof.

[0040] The gum solution may be added with antiseptics or defoamingagents. Examples of antiseptics include phenol and its derivatives,formaline, imidazole derivatives, sodium dehydroacetate,4-isothiazoline-3-one derivatives, benzoisothiazoline-3-one,benzotriazole derivatives, amidinoguanine derivatives, quaternaryammonium salts, derivatives of pyridine, quinoline and guanine, diazine,triazole derivatives, oxazole, and oxazine derivatives. A preferredcontent is a quantity capable of taking stable effect upon bacteria,mold or yeast, depending on the kind of bacteria, molds or yeast. Thecontent is preferably 0.01 to 4% by weight, based on a plate surfaceprotecting agent (or surface protectant). Two or more antiseptic arepreferably used in combination to take effects upon various kinds ofbacteria or molds. Silicone defoaming agents are preferred, and any oneof emulsion type and solubilization type is usable. A defoaming agent isused suitably at 0.01 to 1.0% by weight, based on the gum solution used.

[0041] Further, there may be added chelating agents. Preferred chelatingagents include, for example, ethylenediaminetetraacetic acid and itssodium and potassium salts, diethylenetriaminepentaacetic acid and itssodium and potassium salts, triethylenetetraminehexaacetic acid and itssodium and potassium salts, ethylenediaminedisuccinic acid and itssodium and potassium salts, hydroxyethylethylenediaminetriacetic acidand its sodium and potassium salts, nitrilotriacetic acid and its sodiumand potassium salts, and organic phosphonic acids orphosphonoalkanecarboxylic acids, such as1-hydroxyethane-1,1-diphosphonic acid and its sodium and potassiumsalts, aminotri(methylenephosphonic acid) and its sodium and potassiumsalts. Besides the foregoing sodium and potassium salts of chelatingagents, organic amine salts are also effective. Chelating agents areselected from those which can be stably present in the gum solutioncomposition and is free from adverse effects on printing. The contentthereof is preferably 0.001 to 1.0% by weight, based on the gum solutionused.

[0042] In addition to the foregoing ingredients, alipophilicity-enhancing agent may be incorporated. Examples thereofinclude hydrocarbons such as turpentine oil, xylene, toluene, lowheptane, solvent naphtha, kerosene, mineral spirit, petroleum fractionsexhibiting a boiling point of ca. 120 to 250° C.; and plasticizersexhibiting a freezing point of 15° C. or less and a boiling point of300° C. or more at 1 atmospheric pressure, including phthalic aciddiesters such as dibutyl phthalate, diheptyl phthalate, di-n-octylphthalate, di(2-ethylhexyl)phthalate, dinonyl phthalate, dodecylvdilauryl phthalate, and butylbenzyl phthalate; dibasic fatty acidesters, such as dioctyl adipate, butylglycol adipate, dioctyl azelate,dibutyl sebacate, di(2-ethylhexyl)sebacate, and diocyl sebacate;epoxy-modified triglycerides such as epoxy-modified soybean oil;phosphoric acid esters such as tricresyl phosphate, trioctyl phosphate,and triscrolethyl phosphate; and benzoic acid esters such as benzylbenzoate. Further, there are included saturated fatty acids such ascaproic acid, enatoic acid, heralgonic acid, capric acid, undecylicacid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid,palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid,arachic acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoicacid, montanic acid, melissic acid, lacceric acid, and iso-valeric acid;and unsaturated fatty acids such as acrylic acid, crotonic acid,isocrotonic acid, undecylenic acidpleic acid, elaidic acid, cetoleicacid, nilcaic acid, btecidinic acid, sorbic acid, linolic acid,linolenic acid, arachidonic acid, propiolic acid, stearolic acid,sardine oil, tariric acid, and licanic acid. Of the foregoing, a fattyacid which is liquid at 50° C. is more preferred, one having 5 to 25carbons is still more preferred, and one having 8 to 21 carbons is mostpreferred. These lipophilicity-enhancing agents may be used alone or intheir combination. The content thereof is preferably 0.01 to 10%, andmore preferably 0.05 to 5% by weight, based on the gum. Thelipophilicity-enhancing agents may be incorporated through solution inthe oil phase of a gum emulsion. Alternatively, they may be solubilizedwith the aid of a solubilizing agent.

[0043] A solid concentration of the gum solution usable in thisinvention is preferably 5 to 30 g/l. A gum layer thickness can becontrolled by conditions of a squeezing means of a processor. A gumcoverage is preferably 1 to 10 g/m². A gum coverage of more than 10 g/m²necessitates drying the plate surface at a relatively high temperatureto complete drying for a short period, which is disadvantageous in termsof cost and safety, and whereby effects of this invention cannot besufficiently achieved. A gum coverage of less than 1 g/m² results innon-uniform coating and unstable processability.

[0044] In this invention, the time from completion of coating the gumsolution to start of drying is preferably 3 sec. or less, and morepreferably 2 sec. or less. The shorter time enhances ink affinity.

[0045] The drying time is preferably 1 to 5 sec. Effects of thisinvention cannot be achieved at a drying time of more than 5 sec. Adrying time of less than 1 sec. necessitates raising the plate surfacetemperature to sufficiently dry the lithographic printing plate, leadingto disadvantages in cost and safety. Commonly known drying methods usinga hot air heater or a far-infrared heater are applicable in thisinvention. In the drying stage, solvents included in the gum solutionneed to be dried, necessitating securing sufficient drying temperatureand heater capacity. The temperature needed for drying depends on thecomposition of the gum solution. In the case of the solvent of the gumsolution being water, for example, the drying time is preferably 55° C.or more. The capacity is preferably at least 2.6 kW in a hot air dryingsystem. A larger capacity is desirable and a capacity of 2.6 to 7 kW ispreferred in balance with cost.

[0046] Washing solution used in this invention usually employs water andmay optionally be added with the following additives.

[0047] There are used chelating compounds which are capable of forming achelate compound through coordination-bonding with a metal ion. Examplesof chelating agents include ethylenediaminetetraacetic acid and itspotassium and sodium salts, ethylenediaminedisuccinic acid and itspotassium and sodium salts, triethylenetetraminehexaacetic acid and itssodium and potassium salts, diethylenetriaminepentaacetic acid and itssodium and potassium salts, hydroxyethylethylenediaminetriacetic acidand its sodium and potassium salts, nitrilotriacetic acid and its sodiumand potassium salts, 1-hydroxyethane-1,1-diphosphonic acid and itssodium and potassium salts, aminotri(methylenephosphonic acid) and itssodium and potassium salts and phosphonoalkanetricarboxylic acid.Besides the foregoing sodium and potassium salts of chelating agents,organic amine salts are also effective. These chelating agents arecontained in an amount of 0 to 3.0% by weight.

[0048] Surfactants usable in this invention include any one of anionic,nonionic, cationic and amphoteric surfactants, and anionic and nonionicsurfactants are preferably used. The kind of preferred surfactants isdifferent depending on the composition of an over-coat layer orphotosensitive layer. In general are preferred surfactants which arecapable of promoting dissolution of material used in the over-coat layerand exhibit less solubility for components of the photosensitive layer.

[0049] Examples of anionic surfactants include fatty acid salts, abieticacid salts, hydroxyalkanesulfonates, alkanesulfonates,dialkylsulfosuccinates, straight chain alkylbebzenesulfonates, branchedalktlbebzenesulfonates, alkylnaphthalenesulfonates,alkylphenoxypolyoxyethylene propylsulfonates, polyoxyethylenealkylsulfophenyl ether, polyoxyethylene aryl ether sulfonic acid salts,polyoxyethylene-naphthyl ether sulfonic acid salts,N-metyl-N-oleyltaurine sodium salts, petroleum sulfonic acid salts,nitrated castor oil, sulfated tallow oil, fatty acid alkyl estersulfuric acid ester salts, alkylnitrates, polyoxyethylene alkyl ethersulfuric acid ester salts, fatty acid monoglyceride sulfate ester salts,polyoxyethylene alkylphenyl ether sulfuric acid salts, alkylphosphateester salts, polyoxyethylene alkyl ether phosphoric acid ester salts,polyoxyethylene alkylphenyl ether phosphoric acid ester salts, partiallysaponified styrene anhydrous maleic acid copolymer, partially saponifiedolefin-anhydrous maleic acid copolymer, and naphthalenesulfonateformaline condensates. Of the foregoing, dialkylsulfosuccinates,alkylsulfates and alkylnaphthalenesulfonates are preferred.

[0050] Examples of nonionic surfactants include polyoxyethylene alkylethers, polyoxyethylene alkylphenyl ethers,polyoxyethylene-polyoxypropylene block polymers, polyoxyethylene arylethers, polyoxyethylene naphthyl ethers, polyoxyethylenepolystyrylphenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers,glycerin fatty acid partial esters, sorbitan fatty acid partial esters,pentaerythritol fatyy acid partial esters, propylene glycol monofattyacid esters, sugar fatty acid partial esters, polyoxuethylen sorbitanfatty acid partial esters, polyoxyethylene sorbitol fatty acid partialesters, polyethylene glycol fatty acid partial esters, polyglycerinfatty acid partial esters, polyoxyethylene-modified caster oils,polyoxyethylene grycerin fatty acid partial esters, fatty aciddiethanolamides, N,N-bis-2-hydroxyalkylamines, polyoxyethylenealkylamine, triethanolamine fatty acid esters and trialkylamineoxides.The surfactant is contained preferably in an amount of 0 to 10% byweight. The surfactant may be used in combination with defoaming agents.

[0051] Antiseptics usable in this invention include, for example, phenoland its derivatives, formaline, imidazole derivatives, sodiumdehydroacetate, 4-isothiazoline-3-one derivatives,benzoisothiazoline-3-one, benzotriazole derivatives, amidinoguaninederivatives, quaternary ammonium salts, derivatives of pyridine,quinoline and guanine, diazine, triazole derivatives, oxazole, andoxazine derivatives.

[0052] In washing, a washing solution used prior to development is usedpreferably at a controlled temperature, and more preferably at 10 to 60°C. Washing can be performed using commonly known solution-feedingtechniques such as spraying, squeezing roll and submerged shower in adipping treatment. After completion of the washing stage prior todevelopment, development may be immediately conducted, or drying may beconducted after the washing stage, subsequently, development may beperformed. The development stage is followed by a post-treatment such aswashing, rinsing or a gumming treatment. Washing water used prior todevelopment may also be reused as washing water or for a rinse solutionor gumming solution.

[0053] A photopolymerization type photosensitive composition whichconstitutes the photosensitive layer of the lithographic printing plateaccording to this invention is composed of an ethylenically unsaturatedmonomer, a photopolymerization initiator (hereinafter, also denotedsimply as a photoinitiator) and a polymeric binder as indispensablecomponents, and a variety of compounds, such as a coloring agent, aplasticizer and a thermal polymerization inhibitor may optionally beused.

[0054] The ethylenically unsaturated monomer is referred to as acompound having an ethylenically unsaturated bond, which is capable ofundergoing addition polymerization by interaction with aphotopolymerization initiator to perform cross-linking or hardening whenthe photopolymerization type photosensitive composition is exposed toactinic rays. Such a compound having an ethylenically unsaturated bond,capable of undergoing addition polymerization can optimally be selectedfrom compounds containing at least one (preferably at least two)terminal ethylenically unsaturated bond. Examples thereof includevarious chemical forms, such as a monomer, a pre-polymer (e.g., dimer,trimer, oligomer) and a their mixture or copolymer.

[0055] Ethylenically unsaturated monomers usable in this inventioninclude amides of unsaturated carboxylic acids (e.g., acrylic acid,methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleicacid) and amides of unsaturated carboxylic acids and aliphatic polyaminecompounds are preferred. Unsaturated carboxylic acid esters whichcontain a nucleophilic substituent such as hydroxy, amino or mercaptogroup, and an addition product of amides and monofunctional orpolyfunctional isocyanates are also suitably used in this invention. Anaddition product of isocyanate group-containing unsaturated carboxylicacid esters or amides and monofunctinal or polyfunctional alcohols,amines or thiols; and a substitution product with mono- orpoly-functional amines containing a leaving substituent group such as ahalogen group or tosyloxy group are also suitably usable. In place ofthe foregoing unsaturated carboxylic acids, compounds replaced by anunsaturated phosphonic acid, styrene or vinyl ether are also usable.

[0056] A specifically preferred addition polymerizable compoundcontaining at least one ethylenically unsaturated bond is a urethanetype addition-polymerizable compound prepared through the additionreaction of isocyanate and hydroxy group. Specific examples of such acompound include a vinylurethane compound containing at least twopolymerizable vinyl group, which is obtained by causing a polyisocyanatecompound containing at least two isocyanate groups (e.g., described inJP-B No. 48-41708) to undergo addition to a hydroxy-containing vinylmonomer, represented by the following formula (2):

CH₂═C(R)COOH₂CH(R′)OH  formula (2)

[0057] wherein R and R′ are each H or CH₃.

[0058] There are also cited urethane(metha)acrylates described in JP-ANo. 51-37193 and JP-B Nos. 2-32293 and 2-16765 (hereinafter, the term,JP-B refers to Japanese Patent Publication) urethane compounds having anethylene oxide skeleton described in JP-B Nos. 58-49860, 56-17654,62-39417 and 62-39418. Specifically preferred examples thereof includecompounds, as shown below, which are reaction products of polyisocyanatecompounds of group (1) and alcohol compound of group (2).

[0059] Further, specific compound are as follows: urethaneacrylateM-1100, M-1200, M-1210, and M-1300, available from To a Gosei Co., Ltd.;urethaneacrylate EB210, EB4827, EB6700, EB220, available from DAICEL UCBCo., Ltd.; UVITHAN-782, UVITHAN-783, UVITHAN-788, and UVITHAN-893,available from MORTON THIOKOL Inc.; Art Resin UN-9000EP, Art ResinUN-9200A, Art Resin UN-900H, Art Resin UN-1255, Art Resin UN-5000, ArtResin UN-2111A, Art Resin UN-2500, Art Resin UN-3320HA, Art ResinUN-3320HB, Art Resin UN-3320HC, Art Resin UN-3320HS, Art Resin UN-6060P,Art Resin UN-6060PTM, Art Resin SH-380G, Art Resin SH-500 and Art ResinSH-9832, available from Negami Kogyo Co., Ltd.; NK Oligo U-4H, NK OligoU-4HA, NK Oligo U-4P, NK Oligo U-4PA, NK Oligo U-4TX, NX Oligo U-4TXA,NE Oligo U-6LHA, NK Oligo U-6LPA-N, NK Oligo U-6LTXA, Nk Oligo UA-6ELP,NK Oligo UA-6ELH, NK Oligo UA-6ELTX, NK Olig UA-6PLP, NK Oligo U-8MD, NKOligo U-12LMA, NK Oligo U-12LM, NK Oligo 6HA, NK Oligo 108A, NK OligoU-1084A, NK Oligo U-200AX, NK Oligo U-122A, NK Oligo U-340A, NK OligoU-324A, and NK Oligo UA-100, available from Shi-Nakamura Kagaku Co.,Ltd.; AH-600, At-600, UA-306H, AI-600, UA-101T, UA-101I, UA-101H,UA-306T, UA-306I, UF-8001, UF-8003, available from Kyoei Kagaku Co.,Ltd.

[0060] Specific examples of the foregoing amide monomer of a aliphaticpolyamine compound and an unsaturated carboxylic acid includemethylenebis-acrylamide, methylenebis-methacrylamide,1,6-hexamethylenebis-acrylamide, 1,6-hexamethylenebis-methacrylamide,diethylenetriaminetrisacrylamide, xylylenebisacrylamide, andxylylenebismethacrylamide. In addition, preferred amide monomers includefor example, those having a cyclohexylene structure, as described inJP-B No. 54-21726.

[0061] Further, ethylenically unsaturated monomers usable in thisinvention include reaction produces of a monoisocyanate or diisocyanateand a partial ester of a polyhydric alcohol, as described in West GermanPatent Nos. 2,064,079A, 2,361,041A and 2,822,190A. There are alsosuitably usable unsaturated compounds containing a photoxidizing group,such as a thio group, ureido group or urethane group, which may take ain formation of a heterocyclic ring, e.g., triethanolamine group,triphenylamino group, thioureido group, imidazole group, oxazole group,thiazole group, N-phenylglycine group, ascorbic acid group. Suchcompounds are described in European Patent No. 287,818A, 353,389A and384,735A. Of the compounds described therein, those which contain atertiary amino group, ureido group or urethane group are preferred.These unsaturated compounds may be used alone or in their combination,or may be mixed with a commonly known unsaturated compound such as anester monomer of a polyhydric alcohol and an unsaturated carboxylicacid.

[0062] Monomers of an ester of an aliphatic polyhydric alcohol andunsaturated carboxylic acid include, for example, an acrylic acid ester,methacrylic acid ester, itaconic acid ester, crotonic acid ester,isocrotonic acid ester, maleic acid ester. Specific examples of acrylicacid ester include ethylene glycol diacrylate, triethylene glycoldiacrylate, 1,3-butanedioldiacrylate, tetramethyleneglycol diacrylate,propylene glycol diacrylate, neopentylglycol diacrylate,trimethylolpropanetriacrylate,trimethylopropanetri(acryloyloxypropyl)ether,trimethyloethanetriacrylate, hexanediol diacrylate, 1,4-cyclohexanedioldiacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,dipentaerythritol diacrylate, dipentaerythritol pentaacrylate,dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitoltetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate,tri(acryloyloxyethyl)isocyanulate, and polyesteracrylate oligomer.

[0063] Specific examples of a methacrylic acid ester includeteramethylene glycol dimethacrylate, triethylene glycol dimethacrylate,neopentyglycol dimethacrylate, trimethylopropane trimethacrylate,trimethylolethane trimethacrylate, ethylene glycol dimethacrylate,1,3-butanediol dimethacrylate, hexanediol dimethacrylate,pentaerythritol dimethacrylate, pentaerythritol trimethacrylate,pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate,dipentaerythritol hexamethacrylate, dipentaerythritol pentamethacrylate,sorbitol trimethacrylate, sorbitol tetramethacrylate,bis[p-(3-methacryloxy-2-hydroxypropoxy)phenyl]dimethylmethane, andbis-[p-methacryloxyethoxy]phenyl]dimethylmethane.

[0064] Specific examples of an itaconic acid ester include ethyleneglycol itaconate, propylene glycol itaconate, 1,3-butanedioldiitaconate, 1,4-butanediol diitaconate, tetramethylene glycoldiitaconate, pentaerythritol diitaconate, and sorbitol tetraitaconate.Specific examples of a crotonic acid ester include ethylene glycoldicrotonate, tetramethylene glycol dicrotonate, pentaerythritoldicrotonate, and sorbitol tetracrotonate. Specific examples of anisocrotonic acid ester include ethylene glycol diisocrotonate,pentaerythritol diisocrotonate, and sorbitol tetraisocrotonate.

[0065] Specific examples of a maleic acid ester include ethylene glycoldimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, andsorbitol tetramaleate. There are further cited polyfunctional acrylatesand methacrylates, such as polyester acrylates and epoxyacrylateobtained by reaction of epoxy resin with (metha)acrylic acid, asdescribed in JP-A No. 48-64183 and JP-B Nos. 49-43191 and 52-30490.There are also usable phot-hardenable monomers and oligomers, describedin “Nippon Sechaku Kyokai-shi”, vol. 20, No. 7, page 300t308 (1984). Theforegoing ethylenically unsaturated monomers are used in an amount of 5to 80%, and preferably 30 to 70% by weight, based the photosensitivelayer including the total components.

[0066] Photopolymerization initiators which are contained in thephotosensitive layer of the lithographic printing plate according tothis invention are usable by optimum selection of a variety ofphotinitiators known in patent documents or literature or the combineduse of at least two initiators (photoinitiator system) according to thewavelength used. Specific examples are described below but are by nomeans limited to these. In the case of employing light sources such asvisible rays of 400 nm or more, Ar laser, second harmonic ofsemiconductor lasers and SHG-YAG laser, a variety of photoinitiatorshave been proposed, including, for example, a certain kind ofphotoreducing dyes such as rose bengal, eosine and erythrosine describedin U.S. Pat. No. 2,850,445, or a combination of a dye and an initiatorsuch as a compound initiatot system of a dye and amine compound,described in JP-B No. 44-20189; the combined use of hexaarylbiimidazole,a radiaca generating agent and a dye, as described in JP-B No. 45-37377;a combination of hexaarylbiimidazole and p-dialkylaminobenzilidene,described in JP-B No. 47-2528 and JP-A No. 54-155292; a system of acyclic cis-α-dicarbonyl compound and a dye, described in JP-A No.48-84183; a system of a cyclic triazine and a merocyanine dye, describedin JP-A No. 54-151024; a system of 3-ketocoumalin and a a surfactant,described in JP-A Nos. 52-112681 and 58-15503; a system of abiimidazole, styrene derivative and a thiol, described in JP-A No.59-140203; a system of an organic peroxide and a dye, described in JP-ANos. 59-1504, 59-140203, 59-189340, 62-174203, and JP-B No. 62-1641,U.S. Pat. No. 766,055; a system of a dye and an activated halogencompound, described in JP-A Nos. 63-258903 and 2-63054; a system of adye and a borate compound, described in JP-A Nos. 62-14304462-150242,64-13140, 64-13141, 64-13142, 64-13143, 64-13144, 64-17048, 1-229003,1-298348, and 1-138204; a system of a rhodanine ring containing dye anda radical generating agent, described in JP-A Nos. 2-179643 and2-244050; a system of a titanocene and 3-ketocoumalin, described in JP-ANo. 63-221110; a combination system of a titanocene, a xanthene dye andan addition-polymerizable ethylenically unsaturated monomer containingan amino or urethane group, described in JP-A Nos. 4-221958 and4-219756; a system of a titanocene and a specific merocyanine dye,described in JP-A No. 6-295061; and a system of a titanocene and a dyecontaining a benzopyrane ring, described in JP-A No. 8-334897.

[0067] Recently, a laser at the wavelength of 400 to 410 nm (so-calledviolet laser) was developed and there has been developed aphotoinitiator highly sensitive to the wavelength of 450 nm or less,which is also usable as a photoinitiator in this invention. Examplesthereof include a combination of cationic dye/borate described in JP-ANo. 11-84647; a combination of cationic dye/titanocene, described inJP-A No. 2000-147763; and a combination of carbazole typedye/titanocene, described JP-A No. 2001-42524. In this invention, theuse of titanocene compounds is preferred in terms of sensitivity. Thereare usable in this invention a variety of titanocene compounds, forexample, optimally selected from those described in JP-A Nos. 59-152396and 61-151197. Specific examples of such titanocene compounds includedi-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl,di-cyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophenyl-1-yl,di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrfluorophenyl-1-yl,di-cyclopentadienyl-Ti-bis-2,4,6-trifluorophenyl-1-yl,di-cyclopentadienyl-Ti-bis-2,6-di-fluorophenyl-1-yl,di-cyclopentadienyl-Ti-bis-2,4-di-fluorophenyl-1-yl,di-cyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophenyl-1-yl,di-methylcyclopentadienyl-Ti-bis-2,6-difluorophenyl-1-yl, anddi-cyclopentadienyl-Ti-bis-2,6-difluoro-3-(pyl-1-yl)-phenyl-1-yl. It isalso known that photo-initiating ability can be further enhanced byoptional addition of hydrogen providing compounds, such as thiolcompounds, (e.g., 2-mercaptobenzthiazole, 2-mercaptpbenzthiazole,2-mercaptobenzoxazole) or amine compounds (e.g., N-phenylglycine,N,N-dialkylaminoaromatic alkyl ester) to the foregoing photoinitiator.The photopolymerization initiators described above are used at 0.05 to100 parts, preferably 0.1 to 70 parts, and more preferably 0.2 to 50parts by weight, based on 100 parts by weight of ethylenicallyunsaturated monomer.

[0068] Polymeric binder used in the photosensitive layer of thelithographic printing plate of this invention needs to be not only afilm-forming material but also soluble in an alkaline developer solutionso that organic high polymer compounds are used, which are soluble orswellable in alkaline water. Examples such a high polymer compoundinclude addition polymers with a side-chain containing a carboxylic acidgroup, as described in JP-A No. 59-44615, JP-B Nos. 54-34327, 58-12577,54-25957, and JP-A Nos. 54-92723, 59-53836 and 59-71048, such as amethacrylic acid copolymer, acrylic acid copolymer, itaconic acidcopolymer, crotonic acid copolymer, maleic acid copolymer and partiallyesterified maleic acid copolymer.

[0069] There are also usable acidic cellulose derivatives with aside-chain containing a carboxylic acid group. In addition, a polymercompound in which a hydroxy-containing addition polymer is added with acyclic acid anhydride is also usable in this invention. Specifically, ofthese, [benzyl(metha)acrylate/(metha)acrylic acid/optionally otheraddition-polymerizable vinyl monomer]copolymer and[ally(metha)acrylate/(metha)acrylic acid/optionally otheraddition-polymerizable vinyl monomer]copolymer are suitable. Further,water-soluble organic polymers such as polyvinyl pyrrolidone andpolyethyleneoxide are usable. An alcohol-soluble polyamide and polyetherof 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin are usable toenhance strength of hardened film. Polyurethane resin described in JP-BNos. 7-120040, 7-120041, 7-1200428-12424, and JP-A No. 63-287944 arealso usable in this invention.

[0070] Introduction of a radical-reactive group into a side-chain of theforegoing high polymer compounds can enhance strength of hardened film.Examples of such a group include a functional group capable ofundergoing addition polymerization, such as ethylenically unsaturatedgroup, amino group or epoxy group; a functional group capable ofbecoming a radical upon exposure to light, such as a mercapto group,thio group, halogen atom, triazine structure and onium salt structure;and a polar group, such as carboxy group or imido group. Of theforegoing functional groups capable of undergoing additionpolymerization, an ethylenically unsaturated group such as acryl group,methacryl group, allyl group or styryl group is preferred, and afunctional group selected from an amino group, hydroxy group, phosphonegroup, phosphonic acid group, carbamoyl group, isocyanate group, ureidogroup, ureylene group, sulfonic acid group and ammonio group is alsouseful.

[0071] To maintain developability of the composition, a polymeric binderhaving an optimum molecular weight and acid value is preferred in thisinvention and a polymeric binder having a weight-average molecularweight of 5,000 to 300,000 and an acid value of 20 to 200 isspecifically preferred. An organic high polymer can be mixed at anyamount in the whole composition. However, an amount more than 90% byweight results in unsuitable performance, e.g., in image fastness. Thus,the amount is preferably 10 to 90% by weight, and more preferably 30 to80% by weight. The weight ratio of an ethylenically unsaturated monomerto an organic high polymer (polymeric binder) is preferably within therange of 1/9 to 9/1, more preferably 2/8 to 8/2, and still morepreferably 3/7 to 7/3.

[0072] In addition to the main components described above, it isdesirable to add a mall amount of a thermal polymerization inhibitor toinhibit unwanted thermal polymerization of polymerizable ethylenicallymonomers in the process of preparation or during storage. Suitablethermal polymerization inhibitors include, for example, hydroquinone,p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcathecol,benzoquinone, 4,4′-thiobis(3-methyl-6-t-butylphenol),N-nitrosophenylhydroxylamine cerium (III) salt, andN-nitrosophenylhydroxylamine aluminum salt. The thermal polymerizationinhibitor is added preferably in an amount of 0.01 to 5%, based onsolids of the photosensitive layer. Further, to prevent polymerizationinhibition by oxygen, fatty acid derivatives such as behenic acid andbehenic acid amide may be added to allow to be located on the surface ofthe photosensitive layer in the stage of drying after coating. Suchfatty acid derivatives are added preferably in an amount of ca. 0.5 to10% by weight, based on solids of the photosensitive layer.

[0073] Colorants may be incorporated for the purpose of coloring thephotosensitive layer. Such colorants include, for example, pigments suchas phthalocyanine type pigments (e.g., C.I. Pigment Blue 15:3 15:4,15:6), azo type pigments, carbon black, and titanium oxide; and dyessuch as Ethyl Violet, Crystal Violet, azo dyes, anthraquinone dyes andcyanine dyes. The dye or pigment is incorporated preferably in an amountof 0.5 to 20%, based on the whole composition. In addition, there may beincorporated additives such as inorganic fillers and plasticizers suchas diocyl phthalate, dimethyl phethalate and tricesyl phosphate toimprove physical properties of the hardened film. The amount thereof ispreferably not more than 10%, based on the whole composition.

[0074] The photosensitive layer composition of the lithographic printingplate of the invention is dissolved in various organic solvents in theprocess of coating the composition onto the support, to be describedlater. Examples of solvents usable in this invention include acetone,methyl ethyl ketone, cyclohexane, ethyl acetate, ethylene chloride,tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethyleneglycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycolmonomethyl ether, ptopylene glycol monoethyl ether, acetylacetone,cyclohexane, diacetone alcohol, ethylene glycol monomethyl etheracetate, ethylene glycol ethyl ether acetate, ethylene glycolmonoisopropyl ether, ethylene glycol monobutyl ether acetate,3-methoxypropanol, methoxymethoxyethanol, diethylene glycol monomethylether, diethylene glycol monoethyl ether, diethylene glycol dimethylether, diethylene glycol diethyl ether, propylene glycol monomethylether acetate, propylene glycol monoethyl etheracetate-3-methoxypropylacetate, N,N-dimethylformamide,dimethylsulfoxide, γ-butylolactone, methyl lactate, and ethyl lactate.These solvent may be used alone or in combination thereof. Theconcentration of solids contained in a coating solution is suitably 1 to50% by weight.

[0075] The photopolymerizable composition of the photosensitive layermay be added with a surfactant to enhance coating texture. The coverageof the photosensitive layer is preferably 0.1 to 10 g/m², morepreferably, and still more preferably 0.3 to 5 g/m², in terms of weightafter drying.

[0076] There is provided an oxygen-impermeable protective layer(overcoat layer) on the photosensitive layer to prevent polymerizationinhibition by oxygen. Water-soluble vinyl polymers are preferablycontained in the oxygen-impermeable protective layer. Specific examplesthereof include polyvinyl alcohol and its partial ester, ether oracetals and copolymer containing a substantially unsubstituted vinylalcohol unit (e.g., polyvinyl acetal). Polyvinyl alcohols having asaponification degree of 71 to 100 mol % and a polymerization degree of300 to 2400 are cited. Specific examples thereof include PVA-105,PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST,PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220, PVA-224,PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA-420, PVA-613, L-8,each of which are available from KURARAY CO., LTD. There are alsoincluded polyvinylacetate chloro-acetate or -propionate, andpolyvinylformal, polyvinyl acetal or their copolymer, each having asaponification degree of 88 to 100 mol %. Other useful polymers includepolyvinyl pyrrolidone, gelatin and gum arabic, which may be used alonein combination.

[0077] Solvents for use in coating an oxygen-impermeable protectivelayer of the lithographic printing plate of this invention is preferablywater, which may be mixed with alcohols such as methanol or ethanol,ketones such as acetone or methyl ethyl ketone. The solid concentrationof a coating solution is preferably 1 to 20% by weight. Theoxygen-impermeable protective layer may further be added with commonlyknown additives such as a surfactant to enhance coatability or awater-soluble plasticizer to improve film physical properties. Examplesof such a water-soluble plasticizer include propionamide,cyclohexanediol, glycerin, and sorbitol. There may be incorporatedwater-soluble (metha)acryl type polymer, preferably at a coverage of ca.0.1 to ca. 15 g/m² and more preferably 1.0 to 5.0 g/m², in terms ofweight after being dried.

[0078] Next, there will be described supports used in the lithographicprinting plate according to this invention. Aluminum supports usable inthis invention include dimensionally stable aluminum or its alloys(e.g., alloys of silicon, copper, manganese, magnesium, chromium, zinc,lead, bismuth, or nickel), and aluminum or aluminum alloy-laminated or-deposited plastic film or paper. The thicknes of the support is usually0.05 to 1 mm. There is also usable a composite sheet described in JP-ANo. 48-18327.

[0079] Aluminum supports used in this invention are subjected tosubstrate surface treatments, as described below.

[0080] Graining Treatment

[0081] Graining treatments include mechanical graining, chemical etchingand electrolytic graining. Further, there are usable electrochemicalgraining in which graining is electrochemically performed in anelectrolysis solution of hydrochloric acid or nitric acid; andmechanical graining methods such as a wire-brush graining method inwhich the aluminum surface is scratched with a metallic wire, a ballgraining method, in which the aluminum surface is grained with abrasiveballs and other abrasive material, and a brush graining method in whichthe surface is grained with a nylon brush and an abrasive material. Theforegoing graining methods may be used alone or in combinations thereof.The surface-roughening method usable in this invention is preferably anelectrochemical graining in which graining is electrochemicallyperformed in an electrolysis solution of hydrochloric acid or nitricacid, suitably at a current density of 100 to 400 C/dm². Specifically,electrolysis is preferably performed in a 0.1 to 50% hydrochloric acidor nitric acid solution at a temperature of 20 to 100° C. and a currentdensity of 100 to 400 C/dm² over a period of 1 sec to 30 min.

[0082] The thus grained aluminum support is chemically etched with anacid or alkali. The use of an acid as an etching agent is time-consumingto destroy the fine structure, which is disadvantageous for industrialapplication but an improvement of which can be achieved by using analkali-etching agent. Suitable alkali reagents usable in this inventioninclude sodium hydroxide, sodium carbonate, sodium aluminate, sodiummeta-cinnamic acid, sodium phosphate, potassium hydroxide, and lithiumhydroxide. The preferred concentration and temperature are 1 to 50% and20 to 100° C., respectively, and the aluminum dissolution amount ispreferably 5 to 20 g/m². After completion of etching, acid washing isconducted to remove stains (smut) remaining on the surface. Usable acidsinclude nitric acid, sulfuric acid, phosphoric acid, chromic acid,hydrofluoric acid, and fluoroboric acid. Specifically, preferredsmut-removing methods (de-smutting) which are undergone after theelectrochemical surface-roughening treatment include a method ofbringing the surface into contact with 15 to 65 wt % sulfuric acid at 50to 90° C., as described in JP-A No. 53-12739 and an alkali-etchingmethod described in JP-B No. 48-28123. The surface roughness (alsodenoted as Ra) of an aluminum support used in this invention ispreferably 0.3 to 0.7 μm.

[0083] Anodic Oxidation

[0084] The thus treated aluminum support is further subjected to ananodic oxidation treatment. The anodic oxidation treatment can becarried out in accordance with conventional methods known in the art.Specifically, a direct or alternating electric current caused to flowthrough aluminum in an aqueous or non-aqueous solution of sulfuric acid,phosphoric acid, chromic acid, oxalic acid, sulfamic acid orbenzenesulfonic acid alone or in their combination, thereby forming ananodic oxidation film (or oxide layer) on the surface of the aluminumsupport. The anodic oxidation, which is variable depending on conditionsof the electrolysis solution used, is suitably carried out at anelectrolyte concentration of 1 to 80%, a solution temperature of 5 to70° C., a current density of 0.5 to 60 amp./dm², and a voltage of 1 to100 V over an electrolysis time of 10 to 100 sec.

[0085] Of the foregoing anodic oxidation treatments, anodic oxidation ata relatively high current density in sulfuric acid, as described inBritish Patent No. 1,412,768 and anodic oxidation conducted in aphosphoric acid electrolysis bath, as described in U.S. Pat. No.3,511,661 are preferable. In this invention, the anodic oxidation filmthickness is preferably 1 to 10 g/m². A film thickness of less than 1g/m² easily allows flaws to form on the printing plate, and a filmthickness of more than 10 g/m² needs a large amount of electric powerand is economically disadvantageous. The film thickness is morepreferably 1.5 to 7 g/m² and still more preferably 2 to 5 g/m².

[0086] Further, the aluminum support which has been subjected to thegraining and anodic oxidation treatments may optionally be subjected toa sealing treatment of the anodic oxidation film (oxide layer). Sealingof the oxidation film can be conducted by dipping the substrate into hotwater or hot water containing inorganic or organic salts or by a steamtreatment. The aluminum support may be subjected to a silicate treatmentusing alkali metal silicates or other treatments, such as a surfacetreatment by dipping in an aqueous solution containing potassiumfluorozirconate or phosphate salts.

[0087] On the thus surface-treated aluminum support, the photosensitivelayer composed of the photopolymerizable composition described earlieris coated to prepare a lithographic printing plate. Prior to coating thephotosensitive layer, there may optionally be provided an organic orinorganic sub-layer on the support.

[0088] Using conventional actinic rays such as a carbon arc lamp, xenonlamp, metal halide lamp, fluorescent lamp, tungsten lamp, halogen lamp,helium-cadmium laser, argon laser, FD•YAG laser, helium-neon laser orsemiconductor laser (350 to 600 nm), the photosensitive layer of thelithographic printing plate is subjected to imagewise exposure, followedby being developed to form images on the aluminum plate support. Afterimagewise exposure and before development, the lithographic printingplate may be subjected to a heating process at a temperature of 50 to150° C. over a period of 1 sec to 5 min. to enhance hardening efficiencyof the photopolymerizable photosensitive layer.

[0089] The oxygen-impermeable overcoat layer described earlier isprovided on the photosensitive layer, and there are known a method inwhich the overcoat layer and the unexposed photosensitive layer aresimultaneously removed with a developer relating to this invention and amethod in which the overcoat layer is removed with water or hot water,followed by removing the unexposed photosensitive layer in development.The water or hot water may contain an antiseptics described in JP-A No.10-10754 or organic solvents described in JP-A No. 8-278636.

[0090] Using the developer relating to this invention, development ofthe lithographic printing plate is carried out at a temperature of 0 to60° C. (preferably 15 to 40° C.) in accordance with conventionalmanners, for example, in a manner such that the exposed printing plateis dipped into the developer and rubbed off with a brush. In cases whendevelopment is carried out using an automatic processor, a developer isexhausted in proportion to the processing volume so that developabilitycan be recovered using a replenisher solution or fresh developer. Thethus developed lithographic printing plate is further subjected topost-processing using washing water, a rinse solution containingsurfactants or a finisher solution containing gum arabic, as describedin JP-A Nos. 54-8002, 55-115045 and 59-58431. The foregoing treatmentsmay be used in combination in the post-processing. The processedprinting plate may further be subjected to post-exposure or a heatingtreatment such as burning to enhance plate life, as described in JP-ANo. 2000-89478. The thus obtained planographic printing plate is setonto an offset printing machine employed for high-volume printing.

EXAMPLES

[0091] The present invention will be exemplarily described based onexamples but the scope of the invention is by no means limited to these.

Example 1

[0092] The surface of a 0.30 mm thick 1S aluminum plate was grained byusing a nylon brush (#8) and an aqueous 800 mesh permestone suspensionand then well washed with water. Subsequently, after dipped in anaqueous 10% sodium hydroxide solution at 70° C. for 60 sec. to performetching, the plate was washed with running water, neutralized with 20%nitric acid and then washed. The plate was subjected to electrolyticsurface roughening in an aqueous 1% nitric acid solution at 300coulomb/dm² of a quantity of electricity at the anode, using sine wavealternant current under the condition of VA=12.7 V. The depth of surfaceroughness (designated as Ra) was determined to be 0.45 μm. Subsequently,after the plate was dipped into an aqueous 30% sulfuric acid solution at55° C. for 2 min. to perform de-smutting, an anode was arranged onto thegrained surface in an aqueous 30% sulfuric acid solution at 33° C. andanodic oxidation was performed at a current density of 5 A/dm² for 50sec. The oxide film thickness was 2.7 g/m². On the thus treated aluminumplate, the following photopolymerizable composition (1) was coated so asto give a dry coating weight of 1.5 g/m² and dies at 100° C. for 1 min.to form a photosensitive layer. Photopolymerizable composition (1)Ethylenically unsaturated compound (A1) 1.5 parts Linear organic highpolymer (B1) 2.0 parts Sensitizer (C1) 0.15 parts Photoinitiator (D1)0.2 parts ε-Pthalocyanine (F1) dispersion 0.02 parts Fluorinatednonionic surfactant (Megafac 0.03 PARTS F177, DAINIPPON IN & CHEMICALSINC.) Methyl ethyl ketone 9.0 parts Propylene glycol monoethyl etheracetate 7.5 parts Toluene 11.0 parts A1

B1

[0093] Reaction product of the following:

[0094] On the thus formed photosensitive layer, an aqueous of 3 wt %polyvinyl alcohol (a saponification value of 98 mol %, a polymerizationdegree of 500) was coated so as to give a dry coating weight of 2.5 g/m²and dried at 120° C. for 3 min. to obtain a lithographic printing plate.

[0095] The thus prepared photopolymerizable lithographic printing platewas image exposed at a resolution of 2540 dpi (“dpi” represents thenumber of dots per inch or 2.54 cm) using a CTP exposure apparatus,installed with a FD-YAG laser source (Tigercat, available from ECRMCo.). Subsequently, development was conducted using the followingdeveloper and gumming solution in a CTP automatic processor (PHW 23-V,available from Technigraph Co.), which was provided with a pre-washingsection for removing an oxygen-impermeable layer prior to development, adeveloping section filled with a developer having the compositiondescribed below, a washing section for removing developer attached ontothe printing plate surface and a gumming section with a gumming solutionfor protection of line image areas, having the composition describedbelow. Development was carried out at a developing ttemperature of 28°C. for a dipping developing time of 30 sec. to obtain a planographicprinting plate.

[0096] Using a developer which was prepared by diluting a developercomposition having the following composition with water to make 1 liter,the lithographic printing plate was continuously processed, whilereplenishing a developer replenishing solution at a rate of 50 ml/m²,which was prepared by diluting a developer replenisher concentratehaving the following composition with water to make 1 liter. Afterprocessing 300 m² of the lithographic printing plate, a evaluation wasmade in a running developer solution. Further, a developer compositionwas visually evaluated before and after being diluted with water.Evaluation results are shown in Table 1. Developer composition (1)Potassium hydroxide 0.15 g Potassium carbonate 1.0 g Polyoxyethylenenaphthyl ether (n = 13) 5.0 g Disodium ethylenediaminetetraacetate 0.1 gdihydride Developer composition (2) Potassium hydroxide 0.15 g Potassiumcarbonate 2.0 g Sodium laurate 1.0 g Polyoxyethylene polyoxypropyleneblock 3.0 g copolymer (MW: ca. 10,000, EO ratio: 70%) Disodiumethylenediaminedisuccinate 0.1 g Developer composition (3)* Potassiumhydroxide 0.15 g Potassium carbonate 1.0 g Polyoxyethylene naphthylether (n = 13) 4.0 g Polyoxyethylene naphthyl ether (n = 13) 1.0 gsodium sulfonate Disodium ethylenediaminetetraacetate 0.1 g dihydrate*water content: ca. 5% Developer replenisher composition (1)* Potassiumhydroxide 0.6 g Potassium carbonate 1.0 g Polyoxyethylene naphthyl ether(n = 13) 5.0 g Disodium ethylenediaminetetraacetate 0.1 g dihydride(*water content: 0%; silicate content: 0%) Developer replenishercomposition (2) Potassium hydroxide 0.6 g Potassium carbonate 2.0 gSodium laurate 1.0 g Polyoxyethylene polyoxypropylene block 3.0 gcopolymer (MW: ca. 10,000, EO ratio: 70%) Disodiumethylenediaminedisuccinate 0.1 g (*water content: 0%; silicate content:0%) Developer replenisher composition (3)* Potassium hydroxide 0.6 gPotassium carbonate 1.0 g Polyoxyethylene naphthyl ether (n = 13) 4.0 gDisodium ethylenediaminedisuccinate 0.1 g Polyoxyethylene naphthyl ether(n = 13) 1.0 g sodium sulfonate Disodium ethylenediaminedisuccinate 0.1g (*water content: ca. 5%; water content: 0%) Comparative developersolution (1)* Aqueous potassium silicate solution 40.0 g/l (SiO₂: 26 wt%, K₂O: 13.5 wt %) Potassium hydroxide 4.0 g/l Disodiumethylenediaminetetraacetate 0.5 g/l dihydride Polyoxyethylene naphthylether (n = 13) 20.0 g/l sulfonate Water to make 1 liter *anunconcentrated conventional developer solution (*silicate content: 1%)Comparative developer composition (1)* Aqueous potassium silicatesolution 40.0 g (SiO₂: 26 wt %, K₂O: 13.5 wt %) Potassium hydroxide 4.0g Disodium ethylenediaminetetraacetate 0.5 g dihydride Polyoxyethylenenaphthyl ether (n = 13) 20.0 g sodium sulfonate Water 35.0 g (*watercontent: 60%; silicate content: 10%) Comparative developer composition(2)* Aqueous potassium silicate solution 40.0 g (SiO₂: 26 wt %, K₂O:13.5 wt %) Potassium hydroxide 4.0 g Disodiumethylenediaminetetraacetate 0.5 g dihydride Polyoxyethylene naphthylether (n = 13) 20.0 g sulfonate Solid composition (water content lessthan 1%) obtained by drying the foregoing mixture at 60° C. (silicatecontent: 25%). Comparative developer replenisher composition (1)*Aqueous potassium silicate solution 40.0 g/l (SiO₂: 26 wt %, K₂O: 13.5wt %) Potassium hydroxide 4.0 g/l Disodium ethylenediaminetetraacetate0.5 g/l dihydride Polyoxyethylene naphthyl ether (n = 13) 20.0 g/lsulfonate Remainder is water, pH: 12.3 (*silicate content: 1%) Surfaceprotectant (gumming solution) for 1 liter White dextrin 5.0 wt %Hydroxypropy ether-modified starch 10.0 wt % Gum arabic 1.0 wt %Ammonium primary phosphate 0.1 wt % Sodium dilaurylsuccinate 0.15 wt %Polyoxyethylene naphthyl ether (n = 13) 0.5 wt % Ethylene glycol 1.0 wt% Disodium ethyleneglycoltetraacetate 0.005 wt % Ethyl paraben 0.005 wt%

[0097] TABLE 1 Appearance Sample Developer After Being No. CompositionForm Handling Diluted Imaging Remark 1 Developer paste light, viscous,not so transparent *1 Inv. composition (1) easy to handle liquid 2Developer powder light, easy to handle transparent *1 Inv. composition(2) liquid 3 Developer paste light, slightly hard transparent *1 Inv.composition (3) to handle due to liquid viscousness 4 Comp. Developerliquid heavy, hard to handle transparent *1 Comp. Solution (1) liquid 5Comp. Replenisher separation light, non-usable*³ *5 *2 Comp. composition(1) into solid and liquid 6 Comp. Replenisher solid light, non-usable*⁴*5 *2 Comp. composition (2) 7 Replenisher composition paste light,viscous, not so transparent *1 Inv. (1)*⁶ easy to handle liquid 8Replenisher composition powder light easy to handle transparent *1 Inv.(2)*⁷ liquid 9 Replenisher composition paste light, slightly hardtransparent *1 Inv. (3)* to handle due to liquid viscousness 10 Comp.replenisher liquid heavy, hard to handle transparent *1 Comp.concentrate (1)*⁸ liquid

[0098] As can be seen from Table 1, it was proved that developercompositions and developer replenisher concentrates according to thisinvention produced no problem when diluted with water, resulting innormal images.

What is claimed is:
 1. A developer composition for a lithographicprinting plate comprising on an aluminum plate support a photosensitivelayer which comprises an ethylenically unsaturated monomer, aphotopolymerization initiator and a polymeric binder, wherein thedeveloper composition contains water in an amount of not more than 10%by weight and is substantially free from a silicate.
 2. The developercomposition of claim 1, wherein the developer composition contains waterin an amount of not more than 1% by weight.
 3. The developer compositionof claim 1, wherein the developer composition contains an silicate inamount of not more than 0.5% by weight converted to SiO₂.
 4. Thedeveloper composition of claim 1, wherein the developer compositioncomprises an alkali reagent.
 5. The developer composition of claim 1,wherein the developer composition is in the form of a paste.
 6. Thedeveloper composition of claim 1, wherein the developer composition isin the form of powder or granules.
 7. A developer solution for alithographic printing plate comprising on an aluminum plate support aphotosensitive layer which comprises an ethylenically unsaturatedmonomer, a photopolymerization initiator and a polymeric binder, whereinthe developer solution is obtained by dissolving a developer compositionin water, and the developer composition containing water in an amount ofnot more than 10% by weight and being substantially free from asilicate.
 8. The developer solution of claim 7, wherein the developercomposition contains water in an amount of not more than 1% by weight.9. The developer solution of claim 7, wherein the developer compositioncontains an silicate in amount of not more than 0.5% by weight convertedto SiO₂.
 10. The developer solution of claim 7, wherein the thedeveloper composition comprises an alkali reagent.
 11. The developersolution of claim 7, wherein the the developer composition is in theform of a paste.
 12. The developer solution of claim 7, wherein the thedeveloper composition is in the form of powder or granules.